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/
lookup_unix.go
119 lines (108 loc) · 2.5 KB
/
lookup_unix.go
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// +build darwin freebsd linux netbsd openbsd
// +build cgo
package group
import (
"fmt"
"runtime"
"strconv"
"syscall"
"unsafe"
)
/*
#include <unistd.h>
#include <sys/types.h>
#include <grp.h>
#include <stdlib.h>
static int mygetgrgid_r(int gid, struct group *grp,
char *buf, size_t buflen, struct group **result) {
return getgrgid_r(gid, grp, buf, buflen, result);
}
static char **next_mem(char **mem) {
return ++mem;
}
static int member_count(char **mem) {
int c = 0;
for (; *mem; ++mem) {
++c;
}
return c;
}
*/
import "C"
func lookup(groupname string) (*Group, error) {
return lookupUnix(-1, groupname, true)
}
func lookupId(gid string) (*Group, error) {
i, e := strconv.Atoi(gid)
if e != nil {
return nil, e
}
return lookupUnix(i, "", false)
}
func lookupUnix(gid int, groupname string, lookupByName bool) (*Group, error) {
var grp C.struct_group
var result *C.struct_group
var bufSize C.long
if runtime.GOOS == "freebsd" {
// FreeBSD doesn't have _SC_GETGR_R_SIZE_MAX
// and just returns -1. So just use the same
// size that Linux returns
// TODO: Confirm this!
bufSize = 1024
} else {
bufSize = C.sysconf(C._SC_GETGR_R_SIZE_MAX)
if bufSize <= 0 || bufSize > 1<<20 {
return nil, fmt.Errorf("group: unreasonable _SC_GETGR_R_SIZE_MAX of %d", bufSize)
}
}
buf := C.malloc(C.size_t(bufSize))
defer C.free(buf)
var rv C.int
if lookupByName {
nameC := C.CString(groupname)
defer C.free(unsafe.Pointer(nameC))
rv = C.getgrnam_r(nameC,
&grp,
(*C.char)(buf),
C.size_t(bufSize),
&result)
if rv != 0 {
return nil, fmt.Errorf("group: lookup groupname %s: %s", groupname, syscall.Errno(rv))
}
if result == nil {
return nil, UnknownGroupError(groupname)
}
} else {
// mygetgrgid_r is a wrapper around getgrgid_r to
// avoid using gid_t because C.gid_t(gid) for
// unknown reasons doesn't work on linux.
rv = C.mygetgrgid_r(C.int(gid),
&grp,
(*C.char)(buf),
C.size_t(bufSize),
&result)
if rv != 0 {
return nil, fmt.Errorf("group: lookup groupid %d: %s", gid, syscall.Errno(rv))
}
if result == nil {
return nil, UnknownGroupIdError(gid)
}
}
var members []string
if grp.gr_mem != nil {
members = make([]string, C.member_count(grp.gr_mem))
i := 0
for mem := grp.gr_mem; *mem != nil; mem = C.next_mem(mem) {
members[i] = C.GoString(*mem)
i += 1
}
} else {
members = make([]string, 0)
}
g := &Group{
Gid: strconv.Itoa(int(grp.gr_gid)),
Name: C.GoString(grp.gr_name),
Members: members,
}
return g, nil
}